Fix #276: execute panic on zero results

- If the command refers to items, it is forbidden on zero results
- otherwise the command is allowed to execute all the time

src/bin/main.rs

@@ -152,7 +152,7 @@ fn main() {
                 std::process::exit(0)
             }
             std::process::exit(2)
-        },
+        }
     }
 }
 

src/model.rs

@@ -25,7 +25,7 @@ use crate::reader::{Reader, ReaderControl};
 use crate::selection::Selection;
 use crate::spinlock::SpinLock;
 use crate::theme::ColorTheme;
-use crate::util::{inject_command, margin_string_to_size, parse_margin, InjectContext};
+use crate::util::{depends_on_items, inject_command, margin_string_to_size, parse_margin, InjectContext};
 use crate::{FuzzyAlgorithm, MatchEngineFactory, SkimItem};
 
 const REFRESH_DURATION: i64 = 100;
@@ -339,14 +339,30 @@ impl Model {
     }
 
     fn act_execute(&mut self, cmd: &str) {
+        let item = self.selection.get_current_item();
+        if depends_on_items(cmd) && item.is_none() {
+            debug!("act_execute: command refers to items and there is no item for now");
+            debug!("command to execute: [{}]", cmd);
+            return;
+        }
+
         let _ = self.term.pause();
         self.act_execute_silent(cmd);
         let _ = self.term.restart();
     }
 
     fn act_execute_silent(&mut self, cmd: &str) {
         let item = self.selection.get_current_item();
-        let current_selection = item.as_ref().map(|item| item.output()).unwrap();
+        if depends_on_items(cmd) && item.is_none() {
+            debug!("act_execute_silent: command refers to items and there is no item for now");
+            debug!("command to execute: [{}]", cmd);
+            return;
+        }
+
+        let current_selection = item
+            .as_ref()
+            .map(|item| item.output())
+            .unwrap_or_else(|| Cow::Borrowed(""));
         let query = self.query.get_fz_query();
         let cmd_query = self.query.get_cmd_query();
 

src/previewer.rs

@@ -2,7 +2,7 @@ use crate::ansi::{ANSIParser, AnsiString};
 use crate::event::{Event, EventHandler, UpdateScreen};
 use crate::item::ItemWrapper;
 use crate::spinlock::SpinLock;
-use crate::util::{inject_command, InjectContext};
+use crate::util::{depends_on_items, inject_command, InjectContext};
 use crate::{ItemPreview, SkimItem};
 use derive_builder::Builder;
 use nix::libc;
@@ -142,6 +142,12 @@ impl Previewer {
                         ItemPreview::Text(_) | ItemPreview::AnsiText(_) => unreachable!(),
                     };
 
+                    if depends_on_items(&cmd) && self.prev_item.is_none() {
+                        debug!("the command for preview refers to items and currently there is no item");
+                        debug!("command to execute: [{}]", cmd);
+                        PreviewEvent::PreviewPlainText("no item matched".to_string());
+                    }
+
                     let current_selection = self
                         .prev_item
                         .as_ref()

src/util.rs

@@ -10,10 +10,6 @@ use crate::field::get_string_by_range;
 use crate::item::ItemWrapper;
 use crate::SkimItem;
 
-lazy_static! {
-    static ref RE_FIELDS: Regex = Regex::new(r"\\?(\{ *-?[0-9.,cq+]*? *})").unwrap();
-}
-
 pub fn escape_single_quote(text: &str) -> String {
     text.replace("'", "'\\''")
 }
@@ -301,6 +297,17 @@ pub struct InjectContext<'a> {
     pub cmd_query: &'a str,
 }
 
+lazy_static! {
+    static ref RE_ITEMS: Regex = Regex::new(r"\\?(\{ *-?[0-9.+]*? *})").unwrap();
+    static ref RE_FIELDS: Regex = Regex::new(r"\\?(\{ *-?[0-9.,cq+]*? *})").unwrap();
+}
+
+/// Check if a command depends on item
+/// e.g. contains `{}`, `{1..}`, `{+}`
+pub fn depends_on_items(cmd: &str) -> bool {
+    RE_ITEMS.is_match(cmd)
+}
+
 /// inject the fields into commands
 /// cmd: `echo {1..}`, text: `a,b,c`, delimiter: `,`
 /// => `echo b,c`

test/test_skim.py

@@ -844,6 +844,25 @@ def test_cmd_history(self):
         with open(history_file) as fp:
             self.assertEqual('a\nb\nc\ncd', fp.read())
 
+    def test_execute_with_zero_result_ref(self):
+        """execute should not panic with zero results #276"""
+        self.tmux.send_keys(f"""echo -n "" | {self.sk("--bind 'enter:execute(less {})'")}""", Key('Enter'))
+        self.tmux.until(lambda lines: lines.ready_with_lines(0))
+        self.tmux.send_keys(Key('Enter'))
+        self.tmux.send_keys(Key('q'))
+        self.tmux.until(lambda lines: lines.ready_with_lines(0))
+        self.tmux.until(lambda lines: lines[-1].startswith('> q')) # less is not executed at all
+        self.tmux.send_keys(Ctrl('g'))
+
+    def test_execute_with_zero_result_no_ref(self):
+        """execute should not panic with zero results #276"""
+        self.tmux.send_keys(f"""echo -n "" | {self.sk("--bind 'enter:execute(less)'")}""", Key('Enter'))
+        self.tmux.until(lambda lines: lines.ready_with_lines(0))
+        self.tmux.send_keys(Key('Enter'))
+        self.tmux.send_keys(Key('q'))
+        self.tmux.until(lambda lines: lines.ready_with_lines(0))
+        self.tmux.send_keys(Ctrl('g'))
+
 def find_prompt(lines, interactive=False, reverse=False):
     linen = -1
     prompt = ">"